Since October, the Bureau of Land Management has expanded its operations at two national monuments in southern Arizona, trying to crack down on smugglers and illegal immigrants who trample and trash the pristine desert on their way north from Mexico.

The federal agency has brought in more than a dozen law-enforcement rangers from other states to beef up patrols at the Sonoran Desert National Monument, south of Phoenix, where towering saguaro cactuses, wide-open valleys and flat-topped mountains create one of the most iconic vistas in the Sonoran Desert. The operations also have focused on the Ironwood Forest National Monument north of Tucson.

Because of their remote locations and ample hiding places, the monuments have become superhighways for violent smugglers sneaking drugs and illegal immigrants from the Mexican border into Arizona.

The smugglers have cast off acres of trash and created miles of illegal roads by plowing through the desert with disregard for the fragile vegetation, often using stolen vehicles that are driven until they break down and are abandoned, authorities say.

During seven two-week operations, the agency’s rangers have seized more than 27,000 pounds of marijuana and arrested more than 1,200 illegal immigrants, according to the BLM. That is in addition to the thousands of pounds of drugs and thousands of illegal immigrants arrested by law-enforcement authorities.

The agency also has removed 60 abandoned vehicles, 110 bicycles and more than 24 tons of trash, enough to fill 1,239 garbage bags. And the agency has covered up more than 15 miles of illegal roads.

But some of the agency’s work to protect the pristine desert areas from smuggling activity has caused concern among conservation groups.

Last year, the agency began erecting long vehicle barriers made of welded scrap-steel railroad tracks to block smugglers from driving vehicles through wilderness areas inside the Sonoran Desert National Monument. The barriers have been highly effective, BLM officials say. Not a single smuggler has driven into wilderness areas where the barriers have been installed, they say.

Conservation groups say the barriers, although effective, also mar the landscape. However, they view the barriers as the lesser of two evils.

Monuments under pressure

In 2000, President Bill Clinton created the Sonoran Desert and Ironwood Forest national monuments to protect them from urban sprawl extending south from Phoenix and north from Tucson.

The 487,000-acre Sonoran Desert National Monument is located between Gila Bend and Casa Grande, off Interstate 8. The area is the most biologically diverse desert in North America and is known for its abundant forests of saguaros interspersed with paloverde trees, creosote bushes, sage and ironwood trees.

The area also contains many archaeological and historic sites, including remnants of villages that once belonged to the ancestors of the Tohono O’Odham, Quechan, Maricopa and other Native American tribes.

The smaller Ironwood Forest National Monument encompasses 129,000 acres of desert west of Interstate 10 and north of Tucson. The area is known for its concentration of ironwood trees, some more than 800 years old, and its collection of more than 200 ancient Hohokam sites.

The Sonoran Desert National Monument includes the Vekol Valley, where one man was killed and another wounded in April 2011 during a shooting involving drug smugglers.

The smugglers have carved foot trails that spider through the desert and have left behind acres of plastic water bottles, coats, backpacks and other items cast off after trekking for days from the U.S.-Mexican border to rendezvous points 75 miles to the north along I-8, the main highway smugglers use to transport drugs and illegal immigrants to stash houses in the Phoenix area or to California.

“There is quite a bit of damage done by smugglers,” said Thom Hulen, executive director of the Friends of the Sonoran Desert National Monument, a group that advocates for the monument’s protection. “In addition to all the damage and all the trash, (the smuggling activity) scares people away. They get spooked.”

Signs of smuggling

During a tour of the Sonoran Desert National Monument one recent afternoon, Jon Young, the BLM’s chief ranger in Arizona, pulled his pickup truck off I-8 and stopped next to Mile Marker 157.

He told his passengers to wait in the truck while he got out to make sure there weren’t any drug smugglers hiding in the brush. Young poked around in the brush for a few moments and then gave a thumbs up.

The ground was littered with fresh signs of smuggling activity. Young picked up a boot made of carpeting used by smugglers to conceal their footprints. Strewn nearby were several burlap sacks, remnants of homemade backpacks used for hauling marijuana through the desert.

There were also several mud-caked jackets and lots of empty half-gallon plastic water bottles, colored black to make them less conspicuous in the sunlight.

Young pointed to the ground beneath the bushes, which had been matted down from the weight of smugglers. A well-worn path leading south toward the border also was clearly visible.

Young said smugglers typically hike four or five days through the desert with backpacks loaded with about 45 pounds of marijuana. They usually travel in groups of 10 to 15 but sometimes break into smaller groups.

They also are typically accompanied by a scout who, instead of drugs, carries a backpack full of food, water, radios and cellphones, Young said. Depending on how far the group is traveling, the smugglers may have several support people hiking with heavy packs full of food and extra water, he said.

Once they reach I-8, they hide until other members of the smuggling organization arrive to pick up their loads of drugs. The marijuana is then loaded into pickup trucks and driven to stash houses in nearby towns or the Phoenix area, Young said.

Smuggling has become so prevalent, the BLM has posted signs on roads leading into the monuments that warn the few remaining visitors to travel with caution. The agency doesn’t track visitors, but rangers and conservation groups have seen a decline in the number of hikers and campers who use the monuments, and many now carry guns for protection.

“Smuggling and illegal immigration may be encountered in this area,” the signs say.

Ranger teams

During operations at the monuments, the BLM transfers about 12 to 16 rangers from other states to Arizona. They work with the 10 rangers assigned to the BLM’s Phoenix district, which manages the Sonoran Desert monument, and 12 rangers assigned to the BLM’s Gila district, which oversees the Ironwood monument.

To combat smuggling inside the two monuments, the BLM rangers work with other law-enforcement officers who are part of the Alliance to Combat Transnational Threats, a group of law-enforcement agencies that includes the Border Patrol, Immigration and Customs Enforcement, and the Pinal County and Maricopa County sheriff’s offices.

The most recent operation ended last week, resulting in the collection of 219 bags of trash, the seizure of 6,000 pounds of marijuana and the discovery of the body of one migrant.

On a recent Saturday, Joe Nardinger, 38, a BLM ranger from the Upper Missouri Breaks National Monument in Montana, found 46 bundles of marijuana weighing 1,000 pounds while patrolling a wash on the Sonoran Desert National Monument.

Nardinger, who was sent to Arizona for two weeks, had been following some fresh tire tracks when he found the marijuana. It was hidden in the bank of the wash, covered by branches the smugglers had cut from nearby paloverde and mesquite trees.

“I smelled it before I saw it. I got a whiff, a big dose of it,” Nardinger said.

Installing barriers

In addition to beefed up patrols, the BLM has been cleaning up trash and getting rid of illegal roads and foot trails created by smugglers.

Despite the efforts, drug smuggling continues to increase in the area, although illegal-immigrant traffic is down, Young said.

Their cleanup and restoration work has been applauded by conservation groups. But conservationists are less enthusiastic about the vehicle barriers the BLM has been installing inside the Sonoran Desert National Monument.

Last fall, the BLM erected 1.3 miles of vehicle barriers at the southern end of the Sonoran monument abutting the border of the Tohono O’odham Reservation. They were intended to prevent smugglers from driving north from the reservation through the heart of the monument’s designated wilderness area.

Last week, the agency finished erecting about a quarter-mile of vehicle barriers northwest of the Table Top Mountain Range.

Those barriers are designed to prevent smugglers from driving south from I-8 to rendezvous points inside the monument.

The BLM plans to install more barriers in other parts of the Sonoran monument, Young said.

Known as Normandy barriers, after the coastal barriers used in Nazi-occupied France during World War II, the 2-foot-high barriers have proved effective in preventing smugglers from driving through wilderness areas and creating illegal roads,Young said.

The Border Patrol has installed miles of barriers along the Arizona border with Mexico.

But this is the first time Normandy barriers have been used away from the border, said Matt Skroch, executive director of the Arizona Wilderness Coalition, a conservation group.

The barriers mar the landscape, and conservationists are concerned that those being used inside the Sonoran monument will open the door to more in other pristine desert areas throughout the state, Skroch said.

“We certainly don’t want to see a scenario where we keep installing more and more vehicle barriers,” he said.

But the group isn’t opposed to the barriers outright, Skroch said, because so far, they have been effective in stopping smugglers from creating roads and destroying more of the desert landscape.